Dynamometer



Oct. '19 1926.

J. B. DAVIDSON ET AL.

DYNAMOMETER Filed June 16, 1924 Patented Oct. 19, 1926.

ltll'ffi STATfS JAY BROVNLEE DAVIDSON ANI) EDGAR V.

ATENE" OFFCE.

COLLINS, OF AMES, IOW'A, ASSIGNORS TO IONA STATE COLLEGE OF AGRICULTURE ANB MECHANIC ARTS, OF AMES, IOWA; A

CORPORATION OF IOWA.

DYNAMOMETER.

Application filed June 16, 1924. Serial No. 720,361.

The object of our invention is to provide a device of simple, durable and inexpensive construction for accurately, conveniently and easily testing the tractive power of draft animals, engines and so forth, when advancing over a road surface.

More specifically it is our object to provide a dynamometer of this class which may be operated upon road surfaces of widely different characteristics to suit the requirements for testing draft animals or engines under different road conditions and without having the condition of the road surface in any way affect the accuracy of the dynainometer test.

Our invention consists in the construction, arrangement and combination of the various parts of the device, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in our claims, and illustrated in the accompanying` drawings, in which:

Figure 1 shows a top or plan view of a dynamometer embodying' our invention- Figure 2 shows a side elevation of saine. 'In this ligure the position of the weight when near its upper limit of movement is indicated by dotted lines; and

Figure 3 shows a transverse, vertical,I seetional view on the line 3-3 of Figure 2 the axle and wheels at the top of the figure being shown in elevation.

Referring to the 'accompanying drawings, we have used the reference numeral to indicate the main frame of the dynainometer. This frame is supported near its rear end upon supporting wheels 11 on an axle 12. At the front end the frame 10 is supported on skids 13. This frame and its supporting wheels and skids constitute a vehicle designed to be advanced over a road. surface.

Extended from the front of the frame upwardly and rearwardly at an angle of about thirty degrees to the rear end of the frame are two guides rails 111 preferably formed of channel bars open at their upper ends. Mounted in these guide rails` or inclined track are four wheels 15 rotatably mounted on the axles 16, and these axles in turn support a weight container 17 in which there is detachably mounted a weight 18.

Connected to one of the axles 16 is a cable 19 which extends upwardly and rearwardly and passes over a direction pulley 20 at the upper rear end of the frame 10. The cable from there passes downwardly under a direction pulley 21 at the lower rear end of the frame7 and from thence the cable is extended forwardly under a direction pulley 22 at the front of the frame, and at the front end of said cable is a clevis 23 to which draft animals or a tractive device may be applied.

In practical operation, and assuming that the weight and its container are in their normal position, as shown in Figure 2, with the weight resting upon the frame 10, then the draft animals to be tested are hitched to the clevis Obviously, when the weight is directly over the skids 13, the skids will offer a considerable resistance to the advance of the frame over the road surface, and hence the frame will remain stationary and the entire. tractive force of the draft animals will be applied in elevating the weight upwardly and rearwardly over the inclined track. As the weight progresses up the track, a greater proportion of the weight will be applied to the supporting wheels 11 and a correspondingly decreased proportion of the weight will rest upon the skids. Hence, as the weight advances upwardly and rearwardly, the frictional resistance of the skids relative to the road surface will gradually decrease and at a certain point in the progress of the weight up the incline, the entire frame will commence to advance with the draft animals.

1f the road conditions are such as to create a relatively large amount of friction between the skids and the road surface, the position of the weight while the draft animals are advancing will be substantially as shown by dotted lines in Figure 2, or nearly straight up above the rear supporting wheels. llliereas, if the road conditions are such as to make a minimum amount of friet-ion between the skids and the road surface, the dynamoineter will advance over the road surface when the weight is midway between its upper and lower limit of 1novement.

1f at any time the tractive pull upon the cable should be less than the amount of tractive pull required to elevate the weight, then the weight will descend by gravity to the position shown by solid lines in Figure 2, and will thus apply such great amount of frictional resistance to the skids as to prevent further advance of the dynamometer over the road surface.

As a practical illustration of one of the useful purposes for which our improved dynamometer may be used, let it be assumed that it is desired to test the relative tractive power and endurance of several pairs of draft animals. In conducting this test, one pair of draft animals is attached to the device and then urged to advance. lf the team succeeds in starting the dynamometer, then the operator notes Vthe length of time it requires for the team to move the dynamometer over a measured course. This same test is repeated with the other teams of draft animals entering into the competition.

In practice it frequently happens that so-me of the teams will fail to start the dynamometer, other teams will move it for a few feet and then be unable to advance it further, and if more than one of the competing teams advance it over the full measured course, then obviously the time required for such advance detern'iines which of the teams has the greater tractive power.

ln this connection attention is directed to the fact that the road condition has no appreciable effect in such test because, if the road condition offers a relatively great amount of resistance to the advance of the runners, then the tractve power of the draft animals is applied first in raising the weight, and obviously the position of the weight relative to the runners determines the amount of tractive power that must be applied before the dynamo-meter is advanced, and such advance is therefore not determined by the road condition, nor does the device serve any useful purpose as a means of determining or testing road conditions.

lVe claim as our invention:

l. A dynamometer of the class described, comprising a vehicle, an inclined track carried by the vehicle, its upper end being toward the rear, a weight supported for travel upon said inclined track, a cable connected to the weight and extended `first toward the rear of the vehicle and then toward the front of the vehicle, gui de devices for the cable, and means for applying tractive power to the end of the cable opposite the end that is attached to the weight.

v2. A dynamometer of the class described,

comprising a vehicle, an inclined track carried by the vehicle, its upper end being toward the rear, a weight supported for travel upon said inclined track, a cable connected to the weight and extended first toward the rear of the vehicle and then toward the front of the vehicle, guide devices for the cable, and means for applying tractive power to the end of the cable opposite the end that is attached to the weight, the vehicle including` means for supporting the rear thereof designed to offer a minimum of resistance to the advance of the vehicle and means for supporting the front thereof designed to offer relatively great resistance to the advance of the vehicle.

3. A dynamometer of the class described, comprisingl a frame, an inclined track carried thereby, a weight supported for travel upon said inclined track, means whereby a. tractive force may be applied to said weight to move it upwardly over said inclined track, a supporting means for the frame adjacent to the high end of the inclined track capable of offering only a slight resistance to the advance of the fame, and a supportingr means adiacent to the low end of the inclined track capable of offering a great resistance to such advance.

4L. In a dynamometer of the class described, comprising in combination a frame, a skid at the forward end of the frame, supporting wheels at the rear end of the frame, a track inclined upwardly and rearwardly and supported by the frame, a` weight slidingly mounted upon said track and a cable connected to the weight and extended upwardly and rearwardly over the inclined track and then downwardly and then forwardly to the front end of the device, pulleys carried by the frame and having the cable passed over them, said parts 'being so arranged that when tractive pull is applied to the cable, it will tend to elevate the weight upwardly and rearwardly, and as the weight progresses upwardly and rearwardly, the skids will be relieved of a. portion of the weight and will offer less resistance to the advance of the frame over the road surface, for the purposes stated. Y'

Des Moines, Iowa, March 21, 1924.

JAY BROVVNLEE DAVIDSON. EDGAR V. COLLINS. 

